When performing surgery of the posterior segment of the eye (for example, vitreoretinal surgery), it is typically necessary to view the anatomy of the eye with an operating microscope. Generally, a standard operating microscope is able to view the structures of the anterior segment of the eye and the anterior portion of the posterior segment of the eye, but cannot provide viewing of the entire posterior segment. The reason for this is that the natural optics of the eye (normally consisting of the cornea and the crystalline lens) prevent the operating microscope from focusing on some structures in the posterior segment of the eye such as the retina.
Therefore, in order to focus the operating microscope on structures such as the retina, a vitrectomy lens with the appropriate optical properties is positioned between the eye and the microscope to compensate for the natural optics of the eye. Current vitrectomy lenses are reusable lenses made from optical glass, and in use, are usually held against the eye either with sutures, by hand, or with a silicone ring.